Wissahickon Valley Watershed Association Stormwater Management Techniques


Since its inception more than 50 years ago, The Wissahickon Valley Watershed Association (WVWA) has promoted intelligent land use practices, preservation of environmentally sensitive and historic sites, and has worked on public education initiatives. The WVWA now maintains more than a thousand acres of preserved land in the Wissahickon watershed.

To provide enhanced stormwater management on its properties, WVWA implemented the following BMPs: Porous Paving, a Dry Well, Rain Barrels, and a Constructed Wetland.

Porous Paving 
Plastic pervious paving grids were installed on the grounds of WVWA’s headquarters in 2002 and concrete paving grids were installed in 1991. The earth was leveled at approximately one foot below existing grade and filled with fist-sized stone to create stormwater storage capacity. These grids allow for water and pollutants to penetrate the soil underneath the grid, while still providing structural support for vehicles. Because grass grows within the grid squares, the area is natural looking, retains much less heat than traditional asphalt and reduces the velocity with which stormwater flows off the surface of the ground. Since stormwater has time to percolate into the ground and filter, pollutants associated with parking lots are not washed right off of pavement into waterways. Mowing is the only maintenance work required. Click here for a picture of on site plastic pervious pavement.

Dry Well 
A dry well was built to effectively retain excess drainpipe water during periods of excessive rainfall. To build a dry well the WVWA dug a hole, used grid left over from the pervious parking grid to create a frame, filled the hole with riverstone and placed a 4” PVC pipe on end.

Downspout Disconnect and Rain Barrels 
Rainwater falling on Four Mills Barn is collected from drain pipes and is stored in twin rain barrels. This water is recycled by serving as a reserve for watering plants on site. WVWA disconnects the drain pipes, drains, and seals the rain barrels during the winter to prevent damage from freezing.

Constructed Wetland 
The wetland area along Sandy Run was a strategic area to retrofit because of its high visibility to the public, the high magnitude of stormwater runoff in its vicinity, and the tributary is a contribution of non-point pollution flowing into the Wissahickon Creek. The wetland’s first phase was started in Spring 2006. Trees were planted upstream from the wetland in order to cool the water temperatures in the creek, increasing oxygenation. Within the wetland itself, clay silt, which had been deposited over the years, was removed with the help of heavy machinery. The wetland’s bottom was somewhat staggered in height to create different zones for various aquatic plants. Native wetland vegetation was restored within the basin and a vegetative riparian buffer was created. Since geese are often intrusive and destructive to wetland projects, design strategies to keep them away included tall wetland plants, a vegetative buffer, and geese barriers. Geese barriers, made of stakes and string forming a grid system, also were installed to prevent both geese and deer from consuming juvenile plants.

Interpretive signs are planned to be placed on site in the near future. Other plans for the site include an extension of the Montgomery County Cross Country Trail alongside the wetland.  The wetland’s total area doubled in 2008 with a large-scale expansion project.  For a plant list for the constructed wetland, click here.  The newly planted herbaceous plants are thriving and the newly planted trees and shrubs require watering during their first year before they are established.  The wetland’s maintenance plans over the first five years otherwise include the inspection for and removal of invasive species. In 2009 Galerucella beetles will be released to take care of the purple loosestrife invasion.


County: Montgomery
Watershed: Wissahickon Creek

The Wissahickon Valley Watershed Association (WVWA) is located at 12 Morris Road in the borough of Ambler, Pennsylvania. The WVWA has installed various Best Management Practices (BMPs) on their lands. At Four Mills Barn, the headquarters of the WVWA, several BMPs have been erected around the barn and serve as a model to local commercial and residential proprietors about the ease and utility of their presence. The WVWA also implemented a wetland restoration project along Sandy Run. The Sandy Run stormwater wetland is located in Whitemarsh Township one-tenth of a mile from the R-5 Fort Washington railroad station at a busy intersection at Bethlehem Pike and Lafayette Road. The wetland is a 3-acre restoration project located less than 2 miles from WVWA headquarters and is protected land under WVWA’s stewardship.


PECO Energy
U.S. Environmental Protection Agency
The Environmental Leadership Program


Rain barrels around $160 each
Dry well about $40
Porous pavement from $600-$700 per parking space

The Sandy Run stormwater wetland restoration about $42,000
EPA grant of $40,000


Bob Adams 
Wissahickon Valley Watershed Association
12 Morris Drive
Ambler, PA 19002

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